Flaky test: Increase fetchReport timeout 1s -> 4s

Waiting up to 1s is probably too low. Some bots (mac) are not getting
the expected report on time.

See:
https://bugs.chromium.org/p/chromium/issues/detail?id=1061029#c4

TBR=yhirano@chromium.org

Bug: 1061029
Change-Id: Id3f24cc9ea216e6686ccbb4d534592dd9849a82c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2100931Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749710}

third_party/blink/web_tests/external/wpt/html/cross-origin-embedder-policy/cache-storage-reporting.https.html

@@ -96,11 +96,11 @@ function wait(ms) {
 
 async function fetchReport() {
   const fetch_report_path = resource_path + `/report.py?key=${report_token}`;
-  for(let i = 0; i<10; ++i) {
+  for(let i = 0; i<20; ++i) {
     const response = await fetch(encode(fetch_report_path));
     const reports = await response.json();
     if (reports.length == 0) {
-      wait(100);
+      wait(200);
       continue;
     }
     if (reports.length != 1)